In an electrical communication system, it is sometimes advantageous to transmit information signals (e.g., video, audio, data) over a pair of wires (hereinafter “wire-pair” or “differential pair”) rather than a single wire using balanced transmission techniques. In such systems, the transmitted information signal comprises the voltage difference between the wires without regard to the absolute voltages present. Each wire in a wire-pair is susceptible to picking up electrical noise from sources such as lightning, automobile spark plugs and radio stations to name but a few. Because this type of noise is common to both wires within a pair, the differential information signal is typically not disturbed.
Of greater concern, however, is the electrical noise that is picked up from nearby wires or pairs of wires that may extend in the same general direction for some distance. This noise is referred to as crosstalk. In a communication system involving networked computers, channels are formed by cascading connectors and cable segments. In such channels, the close channels are formed by cascading connectors and cable segments. In such channels, the close proximities and routings of the electrical wires (conductors) and the contacting structures within the connectors can produce capacitive as well as inductive couplings that generate near-end crosstalk (NEXT) (i.e., the crosstalk measured at an input location corresponding to a source at the same location) as well as far-end crosstalk (FEXT) (i.e., the crosstalk measured at the output location corresponding to a source at the input location). The crosstalk induced from the wire(s) of a first differential pair on a second closely spaced differential pair generally comprises an undesired signal that can interfere with the information signal carried by the second differential pair. As long as the same noise signal is added to each wire in the wire-pair, the voltage difference between the wires will remain about the same and differential crosstalk is not induced, while at the same time the average voltage on the two wires with respect to ground reference is elevated and common mode crosstalk is induced. On the other hand, when equal but opposite noise signals are added to each wire in the wire pair, the voltage difference between the wires will be elevated and differential crosstalk is induced, while the average voltage on the two wires with respect to ground reference is not elevated and common mode crosstalk is not induced. The term “differential to differential crosstalk” refers to a differential source signal on one pair inducing a differential noise signal on a nearby pair. The term “differential to common mode crosstalk” refers to a differential source signal on one pair inducing a common mode noise signal on a nearby pair. Uncompensated differential to differential and/or differential to common mode crosstalk can reduce the performance of communications connectors and the communications systems in which such connectors are used.